Conventionally, mattresses configured so as to inflate and deflate a plurality of bladder-shaped cells as appropriate and, for example, prevent decubitus ulcers from occurring in a person lying on the air mattress or improve the contact feel felt by the person have been used as air mattresses. Patent document 1, for example, discloses an air mattress formed by a plurality of bladder-shaped air cells disposed upon a base sheet, wherein all of the air cells are divided into an upper layer and a lower layer by a divider, all of the air cells are respectively inflated or deflated in the upper layers and lower layers thereof, and decubitus ulcers are prevented from occurring in the person lying on the air mattress.
Patent document 2 discloses a technique in which four flexible sheets are layered together, the circumferential edges are bonded together, and the spaces between the flexible sheets are filled with air, thereby constituting an air mattress with three-layered air cells; and the pressure within each of the air cells is separately adjusted, thereby preventing decubitus ulcers from occurring in the person on the air mattress.
Patent document 3 discloses an air cell for an air mattress in which second and third cells smaller in diameter than a single first cell are formed above the first cell, and the first, second, and third cells are in communication with each other. By configuring the air cell in this way, the second cell and third cell increase the area contacting a person when then person lies upon the air mattress, in which a plurality of air cells is lined up, and the second cell and third cell move so as to separate from each other, thus making the air cell as a whole disinclined to collapse and reducing the contact pressure placed upon the person.
Patent document 4 discloses a technique of providing a plurality of air cells within the interior of a retaining member formed of an elastic material so as to line up in the lengthwise direction of an air mattress and adjusting the pressure within the air cells, thereby preventing decubitus ulcers from occurring in a person lying on the air mattress.
Patent document 5 discloses a technique of preventing repelling force from being placed by a mattress upon a location of a person lying on the air mattress at which decubitus ulcers have occurred, and discloses lining up multiple cuboid air cells in the lengthwise direction and widthwise direction of an air mattress, attaching a magnetic marker to a location of a person at which decubitus ulcers have occurred, detecting the position of the marker using a magnetic sensor provided in each of the air cells, and reducing the pressure in the air cells corresponding to the position of the detected marker.